Chapter 10 Internet Connectivity

1. The Complete A+ Guideto PC Repair 5/e Chapter 10Internet Connectivity

2. Chapter Objectives • Describe the difference between serial and parallel data transfer • Configure a serial port and an external modem and all associated system resources and individual settings; configure an internal modem with all associated settings • Define basic handshaking between a DTE device and a DCE device • Use Windows tools to determine which system resources can be assigned to serial devices and determine if they are working properly

3. Chapter Objectives • Explain basic modem concepts and analog modem limitations • Compare and contrast different modems such as analog, cable, digital, fax, satellite, and wireless modems • Perform basic modem troubleshooting • Explain the benefits of mentoring in the IT field

4. Internet Connectivity Overview • Connecting to the Internet • analog modem • ISDN • cable modem • DSL modem • satellite modem • wirelessly • power line • cellular network. • Each of these technologies has its own installation method and configuration, but they all have in common the ability to connect a computer to an outside network. • Each of these technologies is a viable option for connectivity in a specific situation.

5. Modem Overview One of the few serial devices left is a modem. A modem (modulator/demodulator) connects the computer with the outside world through a phone line. A modem converts a signal transmitted over the phone line to digital 1s and 0s to be read by the computer. Modems can be internal or external peripheral devices.

6. Modem Overview 01 02 External Modem Internal Modem • An adapter that normally has 2 ports • Line – to phone jack • Phone – to connect a phone Attaches to a serial port (9-pin male)

7. Serial Communication Overview • Serial devices such as modems transmit or receive information one bit at a time. • In contrast, parallel devices transmit data eight bits at a time. • Serial transmissions are much slower than parallel transmissions because one bit is sent at a time instead of eight. • Serial transmissions can travel longer distances more accurately than parallel transmissions.

8. Serial Versus Parallel Transmissions Figure 10.3

9. Serial Communication Overview Serial Cables No more than 50 feet in length Parallel Cables No more than 15 feet in length Internal or External? The external modem is one of the few serial devices left in use.

10. Serial Communication Overview Asynchronous – Transmissions that do not require a clock signal, but instead, use extra bits to track the beginning and end of data. Synchronous – Transmissions that require the use of a clock signal.

11. Tech Tip – Configuring Transmission Speeds • When configuring the serial port or using an application such as HyperTerminal, the configured speed is the rate at which the serial port transmits. • This is not the speed for an external serial device that connects to the port (such as a modem).

12. Asynchronous Transmission Terms Signals the start of data Start bit Stop bit Signals the end of data EIA standard for the serial port RS232C

13. Asynchronous Transmission Terms Bits per second – A measurement of transmission speed bps The number of times an analog signal changes in one second. Baud Universal Asynchronous Receiver/Transmitter) – A motherboard chip to control the serial port or chip on an internal modem. UART

14. How to Configure Serial Ports and Devices • Serial ports and devices such as internal modems have three important configuration parameters (and others as well, as discussed later): interrupt, I/O (input/output) address, and COM port number. • An internal modem has all these parameters; an external modem uses these same parameters, but they are assigned to the serial port to which the external modem connects.

15. How to Configure Serial Ports and Devices • Each serial port or device must be assigned a different I/O address. • An I/0 address is comparable to a device’s mailbox number so that the processor can differentiate between devices. • No single I/0 address may be shared by two devices. • The assigned I/0 address determines the serial port’s COM port number.

16. How to Configure Serial Ports and Devices • Every serial device or port must also have a different COM port number. • The operating system assigns the serial port a COM port number such as COM1, COM2, COM3, and COM4. • The system BIOS setup program can be used to configure integrated serial ports. • Common BIOS settings include, IRQ, I/0 address, COM port name, and disable.

17. Tech Tip – Application and Hardware Settings Must Match Applications that communicate or control serial devices must have the application settings match the hardware settings or communication will not occur.

18. More Serial Port Settings A software-based method of handshaking that uses special control characters to coordinate transmissions. XON/XOFF A hardware-based method of handshaking that uses signals on specific connector pins to signal the other device when to stop or send data. RTS/CTS Serial devices such as modems, mice and digitizers. They connect to DTE devices. DCE Serial devices such as printers and computers. DTE

19. More Serial Port Settings A setting that determines how many bits make up a data word. Data bits A simple method used to check for data accuracy. Parity The number of bits sent to indicate the end of the data word. Stop bits Used to enable or disable the UART chip’s FIFO buffer. FIFO

20. More Serial Port Settings Flow control Determines how two serial devices communicate The order in which things happen to allow two serial devices to communicate. Handshaking

21. Hardware Handshaking

22. DTE/DCE Signal Connections

23. Serial Device Installation • Installing serial devices can be very frustrating. To avoid problems, install the internal modem or attach the serial device, and determine what COM port, IRQ, and I/0 settings have been assigned to the device. • Check Device Manager to ensure no conflicts have occurred. • Install and configure any software application that controls the device to match these settings. • If the application or device has any self-test feature, use it.

24. Serial Device Troubleshooting • Most serial device problems are IRQ, I/0 address, or COM port related. • The serial device may not be working properly due to the following reasons: (1) configuration setting conflicting with another device; (2) BIOS reassigning the COM port setting; or (3) a software’s configuration setting not matching the serial device setting.

25. Serial Device Troubleshooting • Symptoms for this problem include the following: • The serial device does not work. • A different device quite working. • The serial device works and then locks. • The computer locks during boot up.

26. Serial Device Troubleshooting • Other problems with serial devices are provided in the following list: • Always check the simplest solution first. • If the device is external, check to see if it needs an external power source and, if so, that the external power source is working. • Using the wrong serial cable can cause many problems • Check the system BIOS settings and verify the COM port used by an external serial device is not disabled in Setup, or does not conflict with an internal serial device.

27. Serial Connectivity 1 Straight-through serial cable – used to connect an external modem to a serial port. Null modem cable – used to connect two computers without the use of a modem. 2

28. Pros and Cons of Internal and External Modems • Internal modems require less space than external modem, however they require an expansion slot, generate more heat, and place a larger load on the computer’s power supply. • Internal modems are less expensive than external modems. • External modems connect to an existing serial port. • External modems can easily be connected to a different computer without having to take the computer apart.

29. Pros and Cons of Internal and External Modems • Choosing between an internal and external modem narrows down to the following questions: - Is there an existing expansion slot for an internal modem? - Is there an existing serial port available for an external modem? - Is money an issue? - Is desk space an issue?

30. Modem Speeds and Standards • Modems transmit and receive at different speeds. • A faster modem means less time on the phone line and less time for microprocessor interaction. • However, because modems connect to other modems, the slowest modem determines the fastest connection speed. • A slow modem can only operate at the speed for which it was designed.

31. Modem Speeds and Standards • Communication modem standards are developed by CCITT. For two modems to communicate, they must adhere to the same protocol or set of rules. • Error correction – Standard for the modem to check the data for errors rather than the microprocessor. • MNP (Microcom network protocol) – A set of standards for error correction. • Data compression – A method of converting data into smaller sizes before transmission.

32. Communications Standards

33. 56Kbps Modems • The 56Kbps data transfer rate is only possible if the transmitted (analog) signal converts to digital one time during the data transmission. • Digital phone lines are quieter than their analog counterpart, have less noise on the line, and allow faster data transmissions.

34. General Guidelines for Maximum Modem Speeds

35. Fax Modems • A fax modem allows a modem to use the computer and printer as a fax machine. • Not all computer-based fax machines can handle modem data transfers, however a fax modem does both modem and fax transfers. • The Internet has changed how faxes are transmitted. • Many fax machines can send faxes to email accounts. • VoIP (Voice over IP) – Allows voice traffic to be transmitted over the internet or data networks. Fax machines can have VoIP adapters installed.

36. Modem Installation • Windows has an Install New Modem wizard that automates the modem installation process. • Many technicians avoid using the wizard to detect the modem automatically. Instead, they manually select from the a list of manufacturers and models or use the disk from the modem manufacturer. • The settings can be manually input through the Device Manager.

37. Analog Modem Troubleshooting • In Windows, if the modem is not dialing at all, check the port setting by using the Phone and Modem Options control panel. • Sometimes Windows disables a modem. To verify that the modem is enabled, use Device Manager. • If the modem keeps losing connection, use the prior troubleshooting tips and try placing the modem at a lower speed.

38. Analog Modem Troubleshooting • If the modem is an external unit, turn the modem’s power off and back on, then try the modem again. • If the modem does not dial the number or does not output a dial tone, or if a message appears stating that the modem is not responding, check the phone cord connects to the correct jack on the modem and to the wall phone jack. • If the modem hangs up after some time, other equipment (such as fax machine, answering machines, and portable phones) can be the cause of problem.

39. Analog Modem Troubleshooting • If garbage (random characters) appears on the screen, check the handshaking, parity, stop bit, and baud rate settings. • Verify that the modem works by using the Windows HyperTerminal program. • Another HyperTerminal check is as follows: after setting the modem’s parameters, type ATDT and press . • Type AT&F to restore the factory settings and often solve obscure problems. Enter

40. Analog Modem Troubleshooting • If a letter appears twice on the screen for every letter typed, check the echo mode setting in the communications software package. • If the modem dials, but the high-pitch, screeching noise that indicates connection to another modem or fax does not sound, check the phone number. • Use an external modem’ lights to troubleshoot the problem.

41. Asynchronous Transmission Terms Sometimes called local echo setting; it displays typed commands. Echo mode Sending/receiving data simultaneously. Full-duplex Ability to transmit and receive, but not at the same time. Half-duplex

42. Tech Tip – Modem hangs up or “No dial tone” appears If the modem starts to dial but then hangs up, check to see if the phone cable from the wall jack to the modem inserts into the correct modem jack. This symptom also occurs if the “No dial tone” message appears.

43. Digital Modems and ISDN • Digital modems connect the computer directly to a digital phone line rather than to a traditional analog phone line. • One type of digital phone line available from the phone company is an ISDN line. • ISDN (Integrated Services Digital Network) – A digital phone line that has three separate channels, two B channels, and a D channel. • The B channel allows 64Kbps transmission speeds. • The D channel allows 16Kbps transmissions. • ISDN is commonly used for video conferencing.

44. Cable Modems • Cable modem can be internal or external devices. • If the cable modem is external, two methods commonly exist for connectivity to a PC • A NIC (network interface card) is installed in the computer and a cable attaches between the NIC and the cable modem • The cable modem connects to a USB port. • The USB port is the most common.

45. Cable Modems • Internet data comes in through the cable TV coax cable. • The coax cable plugs into the cable modem. • The cable modem then sends the information out its built-in Ethernet port. • A network cable connects from the cable modem’s Ethernet port into an Ethernet port on the computer. • To send data to the Internet, the reverse happens.

46. Cable Modem Terminology 1 Upstream – Information sent to the Internet such sending an email or uploading a file Downstream – Information pulled from the Internet such viewing Web pages or downloading a file 2 3 Bandwidth – The communications channel width that defines its capacity for carrying data.

47. Cable Modems • The speed of a cable modem connection depends on two things • the cable company • how many people in your neighborhood share the same cable TV provider • The minimum amount of hardware needed to have a cable modem depends on the cable company’s specifications.

48. xDSL (Digital Subscriber Line) Modem • xDSL is another modem technology that is growing in popularity. The x in the term xDSL refers to the various types of DSL that are on the market. • The most common one is ADSL (Asymmetrical DSL), but there are many others. • ADSL uses faster downstream speeds than upstream. This performance is fine for most home Internet users.

49. DSL Technologies

50. DSL Modem Ports